Meteor Crater Helps Unlock Planetary History   
   By Leonard David, SPACE.com's Space Insider Columnist   
   Space.com | SPACE.com - 17 hrs ago   
       
   The Barringer meteorite crater - known popularly as "Meteor Crater" - near   
   Winslow, Ariz., was formed some 50,000 years ago in the flat-lying sedimentary   
   rocks of the Southern Colorado Plateau in Arizona. Now, scientists are using   
   the crater to study mysteries near and far.   
       
   This out-of-the-blue geological feature is considered a prime example of a   
   young, well-preserved and well-documented simple impact crater.   
       
   That means it represents one of the most common morphological features on   
   planetary surfaces, both on Earth, and elsewhere in our solar system.   
   Scientists are using this crater to probe not just our own planetary history,   
   but the mechanics of space rock impacts throughout the universe.   
       
   Meteor Crater is one of very few impact sites on our planet where the geologic   
   details of crater excavation and ejecta emplacement are preserved. While the   
   outline of most simple craters is circular, the shape of Arizona's Meteor   
   Crater strongly deviates from a circle and resembles a quadrangle. [Fallen   
   Stars: A Gallery of Famous Meteorites]   
   "Hole Earth" catalog   
       
   The bowl-shape crater is surprisingly well preserved by terrestrial standards.   
   That makes it a "kiss and tell" terrestrial feature that is being plumbed by   
   researchers far and wide.   
       
   The crater is roughly 0.75 miles (1.2 kilometers) in diameter. That giant hole   
   in the ground sports a rim that rises up to 196 feet (60 meters) above the   
   surrounding landscape. The crater floor falls to a depth of 590 feet (180   
   meters).   
       
   The upper crater walls have average slopes of 40 to 50 degrees, although they   
   also include vertical to near-vertical cliffs. The rock ejected from the   
   crater forms a debris blanket that slopes away from the crater rim out to a   
   distance of 0.6 miles (1 km).   
       
   This impact crater is viewed as a treasured scientific site, not only here on   
   Earth but in shaping future moon and Mars exploration plans. It has become a   
   training ground for astronauts and robot hardware as well as a learning lab   
   for planetary geologists who are investigating impact cratered terrains on   
   other planets.   
       
   Indeed, it's a "hole Earth catalog" of processes that keeps on giving.   
   Honing exploration skills   
       
   When a cosmic interloper slammed into Earth tens of thousands of years ago,   
   more than 175 million metric tons of rock were excavated and deposited on the   
   crater rim and the surrounding terrain in a matter of a few seconds, said   
   David Kring, a senior staff scientist and geologist at the Lunar and Planetary   
   Institute in Houston.   
       
   Kring has been engaged in studies of the crater for decades. He uses the site   
   as a teaching tool for students, as well as a locale for honing the   
   exploration skills to lunge beyond Earth.   
       
   "Those rocks and the processes they record remain the focus of our studies   
   next year," Kring told SPACE.com. "At the same time, we will conduct training   
   activities that are designed to enhance the success of exploration of the moon   
   and planetary surfaces throughout the solar system."   
       
   There are a lot of activities at the crater, Kring said. He made two trips   
   there in October alone, he added.   
       
   Training ground   
       
   First of all, the crater is being used to instruct postdoctoral researchers in   
   the field of lunar science, as well as educate graduate students who are   
   studying impact craters on the moon, Mars, and elsewhere.   
       
   Furthermore, Kring added, Meteor Crater is being used to tutor astronauts for   
   planetary surface operations, which require different talents than those   
   needed for past space shuttle flights and work on the International Space   
   Station.   
       
   In terms of active research, the crater is telling the story of how material   
   is ejected and deposited after a space rock impact. Its revelations have   
   implications for craters on all planetary surfaces.   
       
   Moreover, research at the site is being conducted to determine how water   
   produces gullies and otherwise erodes the crater. This could help scientists   
   interpret observations of Mars.   
       
   Research is also being conducted at Meteor Crater, Kring said, to refine the   
   age of the impact event itself. This work will help calibrate isotopic systems   
   to date geologic events that occur elsewhere in the world.   
       
   Lastly, the crater is providing an on-the-spot opportunity for evaluating the   
   design of traverses and geologic station activities on the moon, Mars and   
   other exploration destinations.   
       
   New questions   
       
   There are still many open scientific questions about the crater itself.   
       
   Kring said that an important remaining problem is that the trajectory of the   
   impacting iron asteroid and the damage it caused to Earth's crust beneath the   
   crater floor remain a mystery.   
       
   "Both might be solved with a shallow drilling campaign," Kring said. Overall,   
   there is still much work to do, Kring said.   
       
   "As we push farther into the solar system, new questions are constantly being   
   developed and require an assessment of new ideas at the world's best preserved   
   impact crater," he said. "Thus, the crater is important for what it can tell   
   us now, but is also important for what it will tell us as we continue to   
   explore beyond low-Earth orbit."   
       
   According to Brad Andes, president of Meteor Crater Enterprises, Inc., this   
   year the crater attracted roughly 225,000 visitors.   
       
   "We are excited about the fact that Meteor Crater has had a very important   
   role as a science research laboratory in the past, but what is even more   
   exciting is that almost every year, researchers request a visit to the crater   
   because of a 'new' question that has been asked," Andes told SPACE.com. "And   
   the answer to that question may live in the crater. This has been happening   
   for decades. I am sure it will continue to happen for many more decades and   
   possibly even centuries."   
       
   There's also potential research at Meteor Crater investigating historical   
   weather events. That information could even have a voice in the global warming   
   debate, Andes said.   
       
   "It is humbling to consider the fact that every day researchers get to work at   
   a place that may be viewed as the Rosetta Stone for astrogeological research,"   
   he said. "This clearly illustrates the need to preserve it to the greatest   
   degree possible while allowing legitimate research to happen here."   
       
   Leonard David has been reporting on the space industry for more than five   
   decades. He is a winner of this year's National Space Club Press Award and a   
   past editor-in-chief of the National Space Society's Ad Astra and Space World   
   magazines. He has written for SPACE.com since 1999.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.64   
    * Origin: NCS BBS (1:3828/7)